1. Field of the Invention
The present invention relates generally to photographic cassettes, and more particularly to a cover latch mechanism for an x-ray film sheet cassette for allowing easy access to the inside of the cassette for cleaning and maintenance.
2. Description of the Prior Art
The cover latch mechanism of this invention is incorporated in an x-ray film sheet cassette of the type disclosed in U.S. Pat. No. 4,444,484. Such a cassette typically has a rectangular solid configuration defined by six orthogonally joined walls which enclose a chamber for accommodating an x-ray film sheet. In one of those walls is a light shielded slot through which a film sheet can pass into and out of the chamber. Within the chamber, in alignment with the slot, is a pair of opposing planar screen surfaces relatively moveable toward and away from each other to prevent and permit, respectively, movement of the film sheet therebetween. One of those surfaces is forced by a spring assembly toward the other to clamp a film sheet therebetween. Means are provided for urging the two surfaces apart in response to placing the cassette into operative relationship with suitably configured film supplying or film processing apparatus, thereby allowing a film sheet to slide between those surfaces when the cassette is positioned for loading or unloading. When so positioned, the cassette is intended to be loaded or unloaded by the simple expedient of letting a film sheet drop into or out of the chamber by force of gravity.
In a prior art end loading x-ray film sheet cassette of the type described, two of the walls thereof comprise opposing front and rear cover walls joined to a pair of end walls and a pair of side walls. While the front cover wall is normally fixed to the end walls and side walls, the rear cover wall is normally slidably moved along grooves in the side walls and into a groove in the opposite end wall into a closed position. The rear cover wall is normally secured in the closed position to the side and end walls by one or more small screws which pass through openings in the rear cover wall and screw into complementary tapped openings in bosses in the side and end walls. Accordingly, to remove the rear cover for allowing access to the inside of the cassette for cleaning and maintenance, it is necessary to obtain a screwdriver of the proper size and type, to unscrew all of the screws, and to slidably remove the cover. Following the cleaning and/or maintenance operation, it is necessary to slidably return the cover to its closed position and to relocate and replace the screws.
Some of the manufacturing problems presented by the prior known means for releasably securing a rear cover wall to the cassette involve designing and precisely positioning tapped openings in the cassette walls, and precisely drilling openings in the rear cover wall in register with the tapped openings. Other problems are that the removal and replacement of the rear cover wall is time consuming, a specialized screwdriver is needed which is not always readily available, and a high risk exists of losing one or more of the small screws. The aforementioned problems are solved by the cover latch mechanism of this invention.